The invention relates to a handheld colour measurement device, especially a handheld spectrophotometer.
Numerous variants of handheld colour measurement devices of the generic type are on the market. The best representatives are, for example, the devices “Eye-One” and “Spectro Eye” of the company Gretag-Macbeth AG, Regensdorf, Switzerland, as well as the devices “Pulse” of the company X-Rite Inc., Grandville, Mich. 49418, U.S.A. and “PrintFix Pro” of the company Datacolor, Lawrenceville, N.J. 08648, U.S.A.
Handheld colour measurement devices of the type discussed herein can be based on any measurement technology. For example, they can be constructed as filter or spectral measurement devices, whereby the latter are the most universal, since as known all of the other parameters of interest in the practice (for example colour values, colour density values etc.) can be derived from the spectral measurement values. The above mentioned known devices are all spectral measurement devices.
Handheld colour measurement devices can furthermore be constructed as autonomous devices or as measurement peripherals for use in connection with a controlling computer. Autonomous handheld colour measurement devices include all control and display structures required for the measurement operation as well as their own power supply and are furthermore additionally often also provided with an interface for communication with a computer, whereby both measurement data as well as control data can be exchanged with the computer. Handheld colour measurement devices designed as measurement peripherals generally have no inherent control and display structures and are like any other computer peripheral—controlled by the superior computer. For communication with a computer, modem handheld colour measurement devices are often provided with a so called USB-interface (Universal Serial Bus), through which in many cases the power supply is simultaneously achieved (from the connected computer). Such a measurement device concept is described, for example, in U.S. Pat. No. 6,590,648 (=EP 1067369 A1).
Handheld colour measurement devices of the generic type can be used for many measurement applications depending on the construction and accessories. The classic base application function is the measurement on coloured substrates, typically a printed product. The handheld colour measurement device is thereby manually positioned on the substrate so that the desired measurement location is located in the field of view (capture region) of the measurement device. Many known handheld colour measurement devices are equipped with aiming aids which facilitate the correct positioning of the device for the user.
A further classic application function is the serial measurement at a multitude of measurement locations on a substrate, typically a colour measurement strip. This application function is normally referred to as Scanning. The handheld colour measurement devices thereby manually guided across the measurement locations, whereby also mechanic guiding devices, for example tracks or the like, can be used.
In a further application function, several known handheld colour measurement devices can also be used for the measurement on monitors. The handheld colour measurement device is thereby manually positioned on the monitor to be measured, whereby it either touches the monitor or is positioned at a small distance therefrom {preferably less than 20 cm). Furthermore, handheld colour measurement devices can in further applications also be used for the measurement of the ambient light or possibly for (remote) measurements on a projection surface which is illuminated, for example, by an electronic projector (beamer). These points are described, for example in EP 1150559 A1 and U.S. Pat. No. 6,590,648 (=EP 1067369 A1).
A special case of application functions consists in the execution of calibration or reference measurements on white or possibly also coloured reference measurement objects (for example a white tile or reference colour surfaces). For example, the handheld colour measurement devices known for this purpose are equipped with incorporated reference measurement objects, which can be manually placed into the measurement beam path. Alternatively, some handheld colour measurement devices are equipped which external reference measurement objects as accessories on which the measurement device can be positioned as in the case of the normal measurement.
Principally, all of the mentioned applications can be realized with most of the known handheld colour measurement devices. However, except for the basic application, more or less significant practical handling difficulties occur in many cases. Either special accessories are required for some applications or the orientation of the measurement device is not possible without auxiliary means or the specific application is overall only relatively laboriously realizable.